1. Field of the Invention
The present invention relates to large trucks wherein the differential of the vehicle is mounted to an axle rather than to the vehicle body, and more particularly, to large trucks wherein the differential carrier housing is sealably mated with a large opening in the axle housing.
2. Discussion of Related Art
Most large vehicles include a wheeled frame that is powered by a front mounted engine. The engine is torsionally connected with a transmission. The output of the transmission is connected with a front drive shaft. A first universal joint is connected between the output shaft of the transmission and a front end of the front drive shaft. A second universal joint is connected between a second end of the front drive shaft and a rear drive shaft. A third universal joint is connected between the rear drive shaft and an input shaft of the differential carrier.
The differential carrier is mounted to the rear axle assembly. The rear axle assembly includes an axle housing which rotatably mounts two half shafts which extend to the driving wheels of the vehicle. The axle housing has a forward-facing central opening to receive the differential which divides torque to the half shafts in an equal fashion when the vehicle is being driven in a straight line and in a preferential, uneven fashion when the vehicle is in a turn.
The differential carrier is mounted in its own housing, which, typically is provided from a stamped metal part. The axle housing has a large, aforementioned central opening and is typically fabricated from a machined casting.
The differential housing has along its perimeter a flange that mounts and seals a flat surface that encircles the central opening of the axle housing. The flange of the differential housing must engage and seal with the axle housing to retain the lubricating grease within the differential and axle assemblies.
The fuel economy of large vehicles, such as trucks, has always been an economic issue. However, in the last quarter-century such issue has taken on a greater importance. Therefore, to maximize the fuel efficiency of trucks there has been a constant quest to reduce the weight of truck vehicular frames and drive line components. Accordingly, there has been a desire to utilize thinner materials in the carrier housing stamping and carrier casting.
Unfortunately, in certain conditions this trend may compromise the sealing capability of the interface between the carrier housing and the axle housing. Previously, a designer of a differential and axle combination for a vehicle was bound to using differential carrier housing made of thicker steel to achieve the sealing capabilities required.